During stand development of conifers like Douglas fir, animals cause the greatest economic damage. Usually the animals browse and clip the stems and foilage of seedlings and saplings; while occasionally root cutting, budding, barking, trampling, and pulling of seedlings occur. Either the seedlings are killed or their growth is markedly suppressed by the browsing of big game (deer, bear, elk, and the like), hares and rabbits, grouse and other birds, beaver, gophers and other small rodents, domestic stock, and porcupines.
Four principal approaches are available for avoiding or controlling animal-caused damage to forest trees and their seedlings:
(1) reduce the animal population; PA1 (2) exclude the animals from the plants mechanically. PA1 (3) repel the animals from browsing; and PA1 (4) alter silviculture practices.
Mechanical protection is the best in terms of damage prevented, but it is among the most expensive safeguards. Silviculture practices include (a) planting resistant species, (b) planting larger seedlings, (c) planting faster growing species, (d) removing and controlling other available food supplies in the plantation which might attract animals, and (e) cutting and replanting in arrangements which deter browsing.
Chemical repellents which affect either odor or taste are of two kinds-systemic and contact. A systemic repellent is applied to the foilage, roots, or soil (in the root zone), is absorbed in to the plant, and is translocated to all parts of the plant. A contact repellent is applied to the foilage and stems of plants and remains on the surface of the plants to treat them. Two common contact repellents are tetramethylthiuram disulfide and zinc dimethyldithiocarbamate cyclohexamine. When used with conifers, these repellents are usually either sprayed onto the plants at the nursery or the plants are dipped prior to planting. Both are usually applied in 10% concentration in a water solution containing latex adhesives, thickening agents, and defoaming agents. Other contact repellents include a putrified fish fraction (PFG), fermented eggs (EV repellent), and human hair.
Systemic repellents have been used extensively in the prior art. Rediske and Lawrence investigated induced animal repellency by using selenate compounds as systemic or contact repellents. 8 Forest Science, Vol. 2, at 142-148 (1962). Sodium selenate applied as surface coating (5,000 ppm Se) was an effective repellent; in fact, is more effective than the standard tetramethylthiuram disulfide contact repellent. As a systemic repellent, however, the experiments of Rediske and Lawrence showed that selenate was a failure. At the maximum allowable concentration in Douglas firs tested, the selenate did not repell animals from browsing.
U.S. Pat. No. 4,388,303, issued June 14, 1983, to George G. Allan, disclosed a method to reduce animal browsing damage to plants. This method comprised the step of inducing a nonphytotoxic dosage of selenium into the foilage of plants at a level sufficient to repel animals. The selenium is systemically absorbed into the plant after application of the surrounding soil in the root zone. By this technique, the roots absorb the selenium and translocate it to the foilage. This technique repelled animals by causing the leaves and foilage of the plants to be distasteful to the browsing animals.
Unfortunately, the prior art methods of utilizing selenium to discourage the browsing of animals was filled with problems. First, a relatively large quanity of selenium compounds was required to induce this systemic absorption. Secondly, insufficient doses, this system absorption of selenium could cause death, rather than discouragement, in certain types of animals. Thirdly, many types of plants are not suited to absorb the chemical selenium. In U.S. Pat. No. 4,388,303, it was believed that the systemic absorption of selenium was nonphytotoxic when the dosage level caused less than one-third of the seedlings to be killed.
The present invention, on the other hand, produces the beneficial effects of dimethyl selenide, without causing these disastrous effects. Through a non-systemic method of producing dimethyl selenide, the browsing animals are strongly are discouraged from entering a newly forested area. Additionally, the deterent effect is created without the destruction of damaging of even a small portion of the plant life in the area treated by the present method.
It is an object of the present invention to provide an animal repellent that effectively prevents the intrusion of many types of animals into newly planted or newly forested areas.
It is another object of the present invention to provide an animal repellent that is safe to human, animal, or plant life.
It is still another object of the present invention that requires a minimum of supervision, maintenance, and installation labor.
It is still a further object of the present invention to provide a method of manufacturing the animal repellent that is highly productive and cost effective.
It is a further object of the present invention to provide an animal repellent that requires relatively low amounts of selenium to be introduced into the area to be protected.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.